In Europe in the 18th century (and before) the Catholic churches often only entered the christening date, not the birth date. Catholic christening usually took place on the day of birth or one day thereafter (Ref. e.g. https://books.google.de/books?id=-uvYWoxLz9EC&pg=PA31&lpg=PA31&dq=Abstand+taufe+geburt+18.+jahrhundert&source=bl&ots=I7F5lkmyKW&sig=TtBV2DD8oLpLrjX8zJoDcuTKYcU&hl=en&sa=X&ved=0ahUKEwiIioCDl7fPAhWHAsAKHX2vDwQQ6AEIHDAA#v=onepage&q=Abstand%20taufe%20geburt%2018.%20jahrhundert&f=false ). This changed around 1800 with the industrialization. They did not have any census.